The present invention related generally to fire suppression systems, and more particularly to a non-toxic fire suppression system, and specifically to a non-toxic fire suppression system for use on aircraft.
Many existing fire suppression systems utilize fluroine containing material sold under the trademark Halon. Because this material is thought to be associated with the depletion of the atmospheric ozone layer, there is a desire to find alternative fire suppression materials. In particular, the United States Federal Aviation Administration is testing alternatives for such chemicals in an effort to certify non-toxic, non-ozone depleting fire suppression systems for use on aircraft.
U.S. Pat. No. 6,003,608 issued on Dec. 21, 1999, teaches a fire suppression apparatus and method for an enclosed space that avoids the use of Halon fire-extinguishing material. That patent teaches the introduction of a non-combustible gas into the enclosed space while expelling the air from the space, thereby smothering the fire. The patent also teaches the introduction of a fire extinguishing dry chemical into the space. Such a system does not provide any mechanism for the removal of heat from the protected space, nor does it address the special requirements for long duration protection against re-flash fires. Furthermore, the use of dry fire extinguishing chemicals can complicate the clean-up after a fire and may result in collateral damage to the protected space and any material stored therein.
Thus there is a particular need for a fire suppression system that can be utilized on an aircraft and that is non-toxic and non-ozone depleting. Such a system must be light weight and must be operable for an extended time period to prevent or suppress any fire re-flash. The collateral damage caused by the operation of such a fire suppression system must be minimized.
Accordingly, the fire suppression apparatus and method described herein provide fire suppression through two mechanisms simultaneously: first by depriving the fire of the oxygen necessary for combustion by flooding the area of the fire with a fire suppressing gas such as nitrogen; and second by cooling the fire through the evaporation of droplets of water suspended in the fire suppressing gas. This is accomplished by delivering the nitrogen and water through a pneumoacoustic atomizer having a resonator in which the flow of nitrogen creates acoustic energy sufficient to break the water flow into a mist of droplets having the desired size range. The nitrogen can be supplied from storage bottles or from a nitrogen generator. The nitrogen generator is supplied with compressed air bled from the turbine engine of the aircraft, thereby ensuring the extended term of operability of the fire suppression system. The volume of water and nitrogen used may be further limited by detecting the location of a fire and thereby providing nitrogen and water to only those pneumoacoustic atomizers proximate the fire. The flow of water to the pneumoacoustic atomizer is delayed for a short period following the initiation of the flow of nitrogen in order to ensure that sufficient acoustical resonance is established in the resonator prior to the introduction of the water.
Thus there is described herein a fire suppression apparatus for an airplane, the fire suppression apparatus comprising: a nitrogen supply comprising bottled nitrogen and a nitrogen generator, the nitrogen generator being supplied with compressed air from a turbine engine of the airplane; a water supply; a pneumoacoustic atomizer connected to the nitrogen supply and to the water supply through a nitrogen control valve and a water control valve respectively, the pneumoacoustic atomizer operable to generate a flow of nitrogen containing a mist of water droplets of a predetermined size range when supplied with nitrogen and water from the nitrogen supply and the water supply respectively; a fire detector; a controller having an input from the fire detector and having outputs operable to control the operation of the nitrogen control valve and the water control valve.
There is further described herein a method of suppressing a fire in an airplane, the method comprising the steps of: providing a supply of nitrogen in the airplane, the supply of nitrogen comprising a bottle of nitrogen and a nitrogen generator; providing a supply of water in the airplane; connecting the supply of nitrogen and the supply of water to a pneumoacoustic atomizer operable to generate a mist of water droplets of a predetermined size range in a flow of nitrogen when supplied with nitrogen and water; detecting the presence of a fire in the airplane; directing the mist of water droplets in the flow of nitrogen toward the fire by initiating a flow of nitrogen and water to the pneumoacoustic atomizer from the nitrogen generator and water supply respectively.